In many downhole applications, it is necessary to run small-diameter conduits or various signal, power, or fiber optic cables downhole for a variety of control and measurement purposes. Frequently, conduits or cables of whatever type must extend past such structures as packers which, when set, completely isolate one portion of the wellbore from another. Various techniques have been used to get conduits and cables past the packing element and setting mechanism of such downhole tools as packers. In some designs, the body of the packer is made additionally thick so that a parallel path can be drilled through the body. This parallel path can literally allow a cable or conduit to pass therethrough with seals on top or bottom. Alternatively, the conduit can be broken at either end of the passage and the passage itself becomes an extension of the conduit. However, this design has the unique disadvantage in that space is limited downhole. Thus, the provision of the additional path or paths to accommodate cables or conduits or both necessarily results in a decreasing available diameter for the main bore through the packer. Thus, a reduction in the I.D. of the bore of the packer, or other downhole tool, limits its usefulness because it restricts flow as well as making it difficult, if not impossible, to pass tools through it to perform procedures further downhole below the tool. Another difficulty with this design is that there are many components that make up the body of the downhole tool, such as a packer. All the components have to be assembled so that the bore in each piece is in alignment so that the conduit or cable can pass through.
Another alternative is to place connectors in the conduit above and below a parallel path through the body of the downhole tool such that the conduit, for example, does not literally pass through the parallel path but terminates at an upper end with a connector and resumes at the lower end of the parallel path with another connector. This has the disadvantage of introducing more connections with potential leakpaths. Additionally, in some applications, thermal loads can become an issue which require coiled sections of the conduit around the downhole tool to compensate for differential expansion.
The use of parallel paths in many cases requires an eccentric design where the main bore through the downhole tool, such as the packer, is off-center to allow room for the various parallel paths for the control lines or cables. Additionally, very long bores under the element of a packer through its body are expensive to fabricate.
In other designs, rotation is required to make up the end connections on at least one end of the downhole tool, with the tubing or cable extending through the tool. This requires the allocation of sufficient slack in the cable or tubing to allow for final make-up. Additionally, in those prior designs, the end connections would not necessarily be designed for torque resistance. Thus, applied torque could stress the line or cable, causing a cut or leak. One such prior design, which breaks the control line and provides a parallel passage while providing no torque resistance on one end where the control line is connected, is the FHL Packer provided by Baker Oil Tools.
Accordingly, one of the objectives of the present invention is to provide an ability to feed the control line or cable through a downhole tool without twisting. Another feature is to minimize orientation issues in feeding the cable or control line through the downhole tool. Another objective is to provide torque resistance which, at the same time, can ease alignment so that the cable or conduit can be simply fed through the downhole tool. Another objective is to provide protection for cables or control lines as they pass through the body of the tool without having to go through a separate and discrete path from the main wellbore, which would in turn reduce the available diameter for the bore through the tool. Another objective is to be able to provide a seal around the cable or conduits. Such seals could also be metal-to-metal, if necessary. Yet another objective is easy passage of single or multiple control lines or cables and increased reliability of objects passing in a conduit since the conduit can be continuous. These and other objectives will be more readily understood by those skilled in the art from a review of the preferred embodiment of the invention described below.